USB_OTG_FS Device Recognition Error

[HMsDobby2]

Hello,
I'm using the nucleo-h743zi2 board.

I am trying to use the USB OTG FS function.

The .IOC file settings are as follows:

• USB_OTG_FS enabled
• MODE: DEVICE_ONLY
• VBUS: disable
• uncheck SOF

I provided power through an external source and also swapped the D+ and D- lines of the USB.

The USB connection LED on the board turns on, but a USB device recognition error occurs in the Device Manager of my computer.

Is there a way to resolve this situation?

[FBL]

Hi @HMsDobby2 

Could you explain why do you swap D+ and D- lines? This is not a common practice and can mess up communication. These lines are differential pairs used for data transmission, and they must be connected correctly for proper operation.

[tjaekel · Accepted solution]

If USB device is not recognized properly, but computer (e.g. Windows) sees "something" (in Device Manager), but does not realize properly what the USB device is...:

The Enumeration went wrong: the USB descriptors sent by the MCU (as device) are not correct or not properly received by the host (computer):

• USB D+ and D- are sensitive signals! (and do not swap!)
  - keep them short as possible
  - make sure they are really "differential signals" on PCB
  - make sure, the impedance for these signals is correct
  - these signals are not "simple digital signals"
  If a wrong PCB design - you can have bit errors.
• check your USB peripheral clock in MCU:
  - is the clock source for USB a good one (precision of OSC/XTAL good enough)?
    (running USB from an internal RC-OSC, like HSI, might never work)
  - is the clock source and PLL config correct? (e.g. using HSE and PLL with correct divider settings for
     USB core clock)?
  If the clock is a bit off or the clock source is not accurate enough - you will get bit errors.
• Check the enumeration:
  - are all the USB descriptors correct?
  - are they all really sent (based on a request to do so sent by the host)?
• Use an USB analyzer on the host computer, e.g. WireShark can debug USB:
  - is the Enumeration received and seen by the host computer "reasonable" (and error free)?

The good news is: your MCU USB seems to send something, but the host PC will not get it error free. Therefore an "unknown device": bit errors or wrong USB descriptors (for Enumeration).

[tjaekel]

BTW:
Even the USB cable length can matter, esp. if the USB traces on your PCB are not really correct (e.g. different length of traces for D+ and D-, not an impedance match).

Check your PCB, use a shorter USB cable, use an USB analyzer...

[HMsDobby2]

I checked and found that the clock configuration settings were incorrect, but now everything is working fine.

Thank you.